Electroplating, electroless plating, electropolishing, or other wet chemical deposition or removal processes employed in semiconductor device fabrication may be performed in “clamshell” apparatuses. The two main components of a clamshell, such as Novellus Systems' Sabre® tool, are a “cup” and a “cone” that form an assembly. Generally, the cup and cone assembly holds, positions, and often rotates a wafer during processing. A lipseal on the lip of the cup may contain embedded contacts for delivering plating current to a seed layer on a wafer. The clamshell provides edge and backside protection to the wafer. In other words, electrolyte is prevented from contacting an edge and backside of a wafer when it is immersed during a plating process. Edge and backside protection is afforded by fluid-resistant seals that are formed when the cup and cone engage one another to hold a wafer.
A plating solution typically includes metal ions in acidic or basic aqueous media. For example, electrolyte may include copper sulfate dissolved in dilute sulfuric acid. During processing, electrical contacts, which deliver plating and/or polishing currents to the wafer and are generally intended to be kept dry by the cup/cone/lipseal hardware combination, can become contaminated with electrolyte and their performance degraded after multiple plated wafer cycles. Electrolyte in the contact area can also be damaging to the wafer, for example, causing particle contamination on the wafer edge.
New apparatuses and methods are needed to reduce plating solution contamination of sensitive clamshell components.